In the previous section we showed strong evidence that emission heights are less than 1000 km for the majority of the radio pulsar population. If we now assume that 1000 km is the maximum allowed emission height, then we can use the width of the profile to provide an upper limit on the value of \(\alpha \)  by combining equations REF  and REF . As an example, it can be seen that for PSR J1842–0359 in Figure REF  the maximum value of \(\alpha \)  is 15. Of the 431 pulsars with good RVM fits, 47 have a maximum allowed \(\alpha \)  less than 45. The cumulative \(\dot{E}\)  distribution of these pulsars is shown in cyan on Figure REF . The distribution is dominated by low \(\dot{E}\)  pulsars, 37 of the 47 have \(\dot{E} < 10^{33}\)  erg s\(^{-1}\)  and only 5 have \(\dot{E} > 10^{35.5}\)  erg s\(^{-1}\) . As lower \(\dot{E}\)  pulsars are older than those with higher \(\dot{E}\) , this result supports an evolution of the magnetic axis towards the spin axis with time, evidence for which is also apparent in other observational studies [1]}, [2]}, [3]} with theoretical underpinning in [4]} and [5]}.
